The present invention relates generally to medical diagnostic methods and devices. More particularly, the present invention relates to a more effective and controlled method of processing a patient blood specimen using a disposable device to displace or dislodge a blood clot in a collection tube to assist in separating the serum from the rest of the blood specimen.
The processing of a patient blood specimen to obtain serum has been a problem for clinical laboratories and specifically for analytical instrument manufacturers supplying products to those laboratories. The need to separate the fibrin clot and cellular matter from the serum, and keeping them separated from each other, remains a continuous and unresolved challenge. In current practice, the closed specimen collection container must be de-capped, manually rimmed (“rimming the clot” to separate the fibrin clot from the container wall using an applicator stick), and then recapped, prior to centrifugation of the specimen container. These processes result in physical, chemical, and biological changes that affect the quality of the serum or otherwise limit its usefulness or condition. Without consistent effective and controlled preparation, analytical quality serum may not be obtained.
The condition of the clotted specimen is dependent on a number of factors including patient condition, additives in the collection tube, the collection technique and the length of time the specimen is allowed to clot, temperature, transport condition etc. Various additives have been used to increase the speed of clot formation and the quality of extracted serum. The clotted specimen may be a loose floating gelatinous mass, mixture of cells, fibrin strands and serum, or a firm clot with the serum trapped below the fibrous surface. To ensure the specimen is not attached to the walls of the container and trapping serum, the specimen tube must be opened and the clot dislodged by mechanical stirring or scraping, called rimming, prior to centrifugation. Opening the tube presents a biohazardous risk to the technician, challenges the integrity of the specimen, and may cause other artifactual changes to the specimen.
A number of methods have been developed to physically separate the constituents. The methods range from the insertion of glass or plastic barriers, to chemical additives to enhance clot formation, or coatings to prevent hemolysis, to the incorporation of gel materials in the collection tube to separate the serum and clot. The specific gravity of the gels is such that after centrifugation, the gel is positioned between the cellular and liquid layers. The use of gels or additives results in the introduction of unwanted, unrelated materials into automated sample transfer systems, and physically occludes the fluidic transfer systems and interferes with further analyses. Present standards require that laboratories verify that these gels do not affect the analysis performed. The ideal preparation method would not require the opening of the specimen tube or the introduction of any foreign material into the specimen.
When a specimen is received for analysis, the sample to be derived from the specimen is identified by the analysis requested. If a serum sample is required, the traditional method of preparation typically requires “rimming the clot” followed by centrifugation. After rimming, the specimen is centrifuged to cause the clot to settle to the bottom of the tube and leaving the serum as the top layer. However, both of these steps can have adverse effects. The rimming process can potentially expose the technician to biohazardous material, and creates biohazardous waste that must be handled and discarded. Additionally, the sample may become contaminated and physical damage caused by this process can result in creating interferents that may affect the analysis. The centrifugation process may also damage the specimen or cause changes in the sample.
There is a need in the art for a more safe effective and controlled method of processing a patient blood specimen. It would be advantageous to provide a clot retainer that can harvest serum from a patient blood collection tube or container without the removal of the septum, cap or stopper. It would also be advantageous to provide a clot retainer that permits the collection or retrieval of serum from the sealed container or collection tube regardless of the condition or physical characteristics of the clotted blood in the container.